Filenames and File Extensions
This section is designed to give you an idea of what file extensions are and what they mean.

Each filename is made up of two parts, the actual name of the file, and what is called the file extension (suffix), the file extension is what the computer uses to identify what type of file it is. You will never normally have to alter file extensions manually, your program/application will usually do it for you, but it is handy to know what they mean.

First of all an example :

anyfile.txt

In this example anyfile is the filename and txt is the file extension (suffix). Notice that the filename and file extension are separated by way of a full stop.

Here is a list of common file extensions and their meanings :

Extension Description
anyfile.bat This is called a batch file and normally contains MS-DOS commands.
anyfile.bmp This is called a bitmap file, it is a graphical image format. 
anyfile.doc This is a Microsoft Word document file.
anyfile.xls This is a Microsoft Excel file.
anyfile.mdb This is a Microsoft Access database file.
anyfile.gif This is another graphical image format typically used on the internet, click here for more info.
anyfile.ini This type of file contains information about the initiation of your system - Never manipulate these files.
anyfile.jpg A graphical image format, click here for more info.
anyfile.sys This is a system file used by the system - Never manipulate these files
anyfile.txt This type of file contains text such as that created with the notepad program in windows.
anyfile.wav This is a wave file, it is an audio file such as the one that plays when you start windows, click here for more info.
anyfile.pdf A file used by Adobe Acrobat Software, click here for more info.
anyfile.mp3 This is a compressed audio file, click here for more info

These are a few examples of file extensions, each program you use i.e your word processor, graphics package, spreadsheet etc, use their own file extensions and you can see these when you save and load files within the program.

Before Windows 98, you could not use long filenames or long directory names, but now all that has changed, so you can be very descriptive when naming files and directories. When naming your files just remember to give them names that you will instantly recognise.